i915: fix missing user_access_end() in page fault exception case

When commit fddcd00a49e9 ("drm/i915: Force the slow path after a
user-write error") unified the error handling for various user access
problems, it didn't do the user_access_end() that is needed for the
unsafe_put_user() case.

It's not a huge deal: a missed user_access_end() will only mean that
SMAP protection isn't active afterwards, and for the error case we'll be
returning to user mode soon enough anyway.  But it's wrong, and adding
the proper user_access_end() is trivial enough (and doing it for the
other error cases where it isn't needed doesn't hurt).

I noticed it while doing the same prep-work for changing
user_access_begin() that precipitated the access_ok() changes in commit
96d4f267e40f ("Remove 'type' argument from access_ok() function").

Fixes: fddcd00a49e9 ("drm/i915: Force the slow path after a user-write error")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: stable@kernel.org # v4.20
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index fee66ccebed63b546d03ebf93c9248379711cfdb..55d8f9b8777fc1156bc0136544f67c5d84e589fa 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1605,6 +1605,7 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb)
                                             (char __user *)urelocs + copied,
                                             len)) {
 end_user:
+                               user_access_end();
                                kvfree(relocs);
                                err = -EFAULT;
                                goto err;